The term "pin grid array" is generally understood to describe a connecting device for connecting the leads from a component to conductors on a circuit board. The pin grid array comprises a plate-like insulating member having oppositely facing major surfaces and having a plurality of holes extending through the insulator with the holes located in accordance with a pin grid pattern. Each of the holes has a socket assembly mounted therein, each socket assembly having a receptacle portion which is adjacent to the first surface of the insulator and a post portion extending from the second surface. The post portion is of reduced diameter, relative to the socket portion, and is intended to be wave soldered to a conductor on the circuit board. The receptacle portion receives a lead from the component when the component, with a plurality of leads extending therefrom, is coupled to the pin grid array.
The socket assemblies are sometimes manufactured as one piece stamped and formed members with the post members integral with the socket members. A problem sometimes encountered with stamped and formed socket devices is that when the pin grid array is mounted on the circuit board, and the post members are wave soldered to the circuit board conductors, the solder may move into the receptacle portions of the socket members by capillary action. The socket or receptacle portion has spring members therein which are intended to establish contact with the component leads and if these spring members are soldered to each other, the socket portion cannot function as it is intended. The higher quality socket assemblies used in pin grid arrays commonly comprise two parts, a separate socket contact or receptacle contact and an enclosure for the socket which may be referred to as a cup. The enclosure has a cylindrical portion which is mounted in the hole in the insulating body and an integral post which extends from the insulating body, the separate socket contact being contained in the enclosure or cup. The highest quality socket assemblies have seamless (rather than stamped and formed) receptacle contacts therein which are manufactured by screw machine methods or by drawing. Because of the fact that the seamless contact socket is contained in an enclosure, there is no possibility for solder to travel into the contact socket area and interfere with its intended function.
Composite socket devices as described above thus have a relatively large diameter portion which receives the seamless contact member and a greatly reduced diameter integral post portion. The relatively large diameter portion which receives the contact socket must be of some minimum length which is substantially greater than the length as measured along the center line thereof of the seamless socket member for the reason that when a component lead is inserted into one of the composite socket devices, sufficient space must be allowed for the lead to pass through the seamless contact member and permit it to extend for a distance beyond the spring tynes of the contact member. This requirement in effect determines the minimum height of the pin grid array when the pin grid array is mounted on a circuit board and under some circumstances, it would be highly desirable to reduce the distance between the surface of the circuit board and the surface of the pin grid array which is opposed to the component when the component is coupled to the pin grid array. In other words, it would be desirable to reduce the profile of the pin grid array with respect to the surface of the circuit board.